Alkaline dry cell



A ril 1, 1958 J. J. COLEMAN ET AL 2,829,189

ALKALINE DRY CELL Filed Aug. 24, 1956 26- a I 45 -12 Q0 5 -30 UnitedStates Patent ALKALINE DRY CELL v Joseph I. Coleman and Paul G. Kort,Freeport, 111., as-

signors to Burgess Battery Company, Freeport, 111., a,

corporation of Delaware Application August 24, 1956, Serial No. 606,0873 Claims. (Cl. 136-107) This invention relates to current-producingprimary electric cells, and'particularly to dry cells having an aqueousalkaline electrolyte.

In alkaline dry cells of the type described, gas is normally generatedvwithin the cell while it stands on open circuit and if such gasformation is not controlled, excessive pressure is created within thecell such that rupture of the cell enclosure takes place, or if suchrupture does not occur, the gas pressure forces open the seal oftheenclosure. In either event, escape of gas takes place regardless ofthe mechanical means employed to prevent such escape, and this isaccompanied by escape of liquid components from the cell, which is thewellknown and objectionable phenomenon of cell leakage.

It is the principal object of the invention to provide a dry cell of thecharacter describedin which the forma-- tion of gas within the cell isinhibited, with the result that excessive internal gas pressure isprevented and cell leakage is avoided.

Other objects of the invention will become apparent from the followingdescription of an embodiment of the dry cell of the invention, whichdescription is to be read in conjunction with the accompanying drawingshowing an example of such acell, in whichvention, there are twoopen-top cups 12 'and arranged in mutually telescoping relation to formthe enclosure for the cell. The inner cup 12 is composed of a suitablemetal'such as steel and has its open top directed downwardly and has themajor central portion of its bottom dished upwardly as shown to form thedished portion 14. Between' the dished portion and the cylindrical wallof inner cup 12is the annular'shoulder'17. The exterior surface of steelcup 12 may be nickel-plated if desired.

The interior surface of the dished portion 14 has an adherent coating 16of zinc thereon, formed by plating "or other suitable method. Withinsaiddished portion 14 and resting in contact with zinclayer 16'is thenegative electrode or anode 18 of the cell, said anode being composed ofamalgamated zinc and preferably being in the form of a body ofcompressed amalgamated zinc,

particles. The amalgamated zinc powder is pressed into the dishedportion 14 under sufiicient pressure that it remains firmly in place.

The outer cup 20 is composed of a suitable metal such as steel and hasits open top directed upwardly. The exterior surface of steel cup 20 maybe nickel-plated if desired. Between the cylindrical edge of the opentop of inner cup 12 and the bottom wall of outer cup 20 is an annularsealing gasket 22 of a suitable sealing composition such as neoprene,polyethylene, or polyvinyl chloride. Such gasket 22 is shaped in crosssection in the form of a deep, narrow U, the base of the U being underpressure between the edge of the inner cup 12 cup'34 which is alsocomposed of steel.

I 2,829,189 Patented Apr. 1, 1958 and the bottom of the outer cup 20,the outer leg of the U extending upwardly in contact with the'exteriorsurface of the cup 12 within the space between said cup and outer cup20, and the inner leg extending upwardly in contact with the interiorsurface of said cup 12.

The upper end portion of the cylindrical wall of outer cup 20 is turnedinwardly to form the flange 24 which clamps the two cups 12 and 20together. An annular gasket 26 composed of vulcanized fibre, modifiedpolystyrene, or other suitable inert non-yielding material is arrangedbetween shoulder 17 and flange 24, said flange being turned down upongasket 26 with sufiicient pressure to hold inner cup 12 in sealingengagement with gasket 22 to form "a substantially liquidandgas-tightseal. Gasket 26' holds the inner and outer cups apart to electricallyinsulate them and to provide the annular space 28 within which is themass of absorbent material 30 which may be absorbent paper such asblotting paper. A small'opening 32 may be provided in the cylindricalwall of outer cup 20 to serve as a gas vent to atmosphere. Within outercup 20 and fixed to the bottom wall of the latter as by welding orsoldering is a third open-top The exterior diameter of cup 34 isslightly less than the interior diameter of cup 12 to leave a narrowannular space between the two members. Cup 34 is shallow in relation tothe'height of cups 12 and 20 to leave a substantial space'between thetop of said cup 34 and the surface of anode 18. I

Within cup 34 is the depolarizing cathode 36 which is composed of amixture of powdered suitable oxygenyielding substance such as mercuricoxide, mercurous oxide, silver oxide, silver peroxide, cupric oxide,cuprous oxide, or other readily-reducible oxygen-yielding compound, ormixtures of such compounds, and a suitable conductive substance such asmicronized graphite. The proportion of conductive substance may bevaried from approximately 5% to approximately 15% by weight of thedepolarizer composition, the remainder being oxygenyielding substance.An example of a preferred de polarizer composition is one containing 90%by weight of powdered mercuric oxide and 10% of micronized graphite. Thedepolarizer composition is compressed into cup 34, the amount ofcomposition being sufficient 'to fill cup 34 substantially level withthe top'edge thereof.

Resting upon the top surface of the depolarizing cathode 36 and theupper edge of cathode cup 34 is'a relatively thin barrier disk 38 of asuitable ionically permeable material such as parchment paper,vinylidine resin, vinyl resin, or other suitable ionically permeablematerial which is resistant to the cell electrolyte and depolarizer. Theedge of said disk 38 extends outwardly beyond the "side wall of cup 34and into contact with gasket 22.

.Above the barrier disk 38 is the electrolyte-receptive body '40 whichis composed of a suitable porous, absorbent electrolyte-resistantmaterial, such as a body of matted cellulose fibers, which may be woodor cotton fibers. The body 40 is of cylindrical shape and preferably hasa diameter smaller than the internal diameter of inner cup 12 whereby anannular space is left between the cup 12 and the body 40. The body 40 isunder compression between the anode 18 and the barrier disk 38 and issufiiciently porous as to be highly absorbent of the liquid electrolyteof the cell.

The electrolyte of the cell is contained in absorbed condition in theabsorbent body 40. The electrolyte is an aqueous solution of a suitablealkaline substance, such as potassium hydroxide, sodium hydroxide,lithium hydroxide, or mixtures of such hydroxides. The amount ofelectrolyte and the proportions of alkali metal hydroxide therein mayvary. By way of example, an amount of electrolyte equal to approximately20% to 25% performance.

stances which are in solutio'nltherein. l the barrier 38 is liquidandion-permeable. The electro- As used herein, and inthe claims appendeterm aluminum oxide. is deemed to i of th'e'weight ofthedepolarizer andan aqueous solu tion containing approximately 35% to 43% of KOH in waterhave been used and found to give satisfactory The barrier disk 38 miilitely porous and is p ermeable to' the liquid ofthe electrolyte: and tothe sub- In other words,

lyte' and the ions thereof freely traverse said barrier but particles ofthe .depolarizer mixture 36 and of the anode 18 are prevented frompassage therethruogh. The electrolyte-receptive element 40 is morecoarsely porous and acts as a reservoir or medium fo -holding theelectrolyte in a sub stantiallyimmobilizedjcondition,

In accordance with th'e present invention, a'substance is incorporatedin' theelectrolyte which has the property of inhibiting gasformatio'nduring periodswhen the cell stands on opencircuit, substance whichiha slbeen found to exert a pronounced effect in inhibiting? such gasformation is aluminum oxide, Al O TheYhydfrous 7 form of aluminum oxide,Al,O '.3H O, sometimesQdesignated as aluminum hydroxide, Al(OH jandotherhydrates of aluminum oxide are suitable for'. the lpurposes of theinvention and effectively inhibit gas formation. ereto, the l "clude thehydrous forms thereof, including aluminum hydroxide 'lfl desired,

the gas inhibiting substance maybe initially lntroduced into theelectrolyte as anhydrous aluminum '0 stance is required to accomplishthe functionoflmilibiting gas formation. Anhydrous aluminum oxidejisonly slightly soluble in the alkaline electrolyte, as 1; pla scontaining 37% by weight of KOH and. 63% being saturated by 0.086 gramAlo' in 100" f water ms of electrolyte. In otherwords a saturated solutioncontains .086%"Al,05 in solution. Desirable 'gas inhibiting res ults areobtained by the use of aluminum oxides i if ficient in ainountto providefrom to 100% saturation of the electrolyte, a range offrom0.0043 to0.086 gram of aluminum oxide per 100 grams of electrolyte.

The mechanism by which the function of gas formation is accomplished isnot understood, but this desirable result has been confirmed byexperimentation.

The, gasket 22 forms a seal between the inner and If such escaping gasis accompanied by cell exterior of the. cell,

1 During operation of the cell, the anode 18 expands in size andmaintains the electrolyte-receptive body 40 under compression'whe'rebythe internal resistance is maintained at a low value.

In a comparative test to demonstrate the efliectiveness of the aluminumoxide in inhibiting gas formation in a preferred mode of practicing theinvention, two batches of cells were constructedhaving the structureshown in Figs. 1 and 2 and having outside dimensions of Wm inch heightand 1 inch diameter, and having as electrolyte an aqueous solutioncontaining 37% of KOH and as depolarizingcathode a mixture of 90% ofHg() and 10% of micronized graphite. The structure of the cells and thecomponents thereof were identical except that in one batch theeletcrolyte was saturated with anhydrous aluminum oxide and in the othersuch oxide was omitted.

All of the cellswere allowed to stand on open circuit at roomtemperature. After 2 hours, one of the cells which did not containaluminum oxide in its electrolyte exuded liquid due toexcessive'internal"ga's pressure,

and the other cells of the same batch similarly failed for of cellscontaining the aluminum oxide in the electrolyte showed no evidence ofexcessive internal gas pressure when 6 months"old,,and the Zincanodesshowed no corrosionl. All of the cells when tested individually onclosed circuits, initially delivered .05-.06 ampere through a resistanceof 20 ohms, and after 6 months standing on open circuit, thecellscontaining aluminum oxide in the electrolyte delivered .05-.055 amperethrough the same resistance.

Invention is claimed as follows:

1. Ina dry cell, anamalgamated zinc anode, a readily- "reducibleoxygen-yielding depolarizingcathode and an alkaline electrolytecontaining aluminum oxide in an amount from'about 0.0043 to about 0.086gram per 100 grams of electrolyte dissolved therein as a means forinhibitinggas formation. 7 v R g g 2. In a dry cell, an amalgamated zincanode, a depolariiing cathode comprising mercuric oxide, and an alkalineelectrolyte containing aluminum oxide in an amountfrom about 0.0043 toabout 0.086 gram per 100 grams of electrolyte.

3. In a dry cell, an amalgamated zinc anode, a depolarizing cathodecomprising mercuric oxide, and an alkaline electrolyte containingpotassium hydroxide and aluminum oxide in an amount from about 0.0043 toabout 0.086 gram per 100 grams of electrolyte.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Bailar, Jr., J. C.: fEssentials of General Chemistry, D. C.Heath & Co., Boston, 1946, pp. 400-1.

1. A DRY CELL, AN AMALGAMATED ZINC ANODE, A READILYREDUCIBLEOXYGEN-YIELDING DEPOLARIZATING CATHODE AN AN ALKALINE ELECTROLYTECONTAINING ALUMINUM OXIDE IN AN AMOUNT FROM ABOUT 0.0043 TO ABOUT 0.086PER 100